I like to try and keep my paint table fresh with different challenges to keep my painting skills progressing; to this end I do like to paint 75mm models from time to time as the different scale provides a diffferent challenge with painting.
One of the great things about 75mm models is that they make brilliant presents for family/friends, which is where this Roman Legionary, affectionately named "Minimus" has ended up, taking his final guard at the top of the stairs.
Primarily Scale 75 colours were used as they provide more natural tones suitable for a histrorical model - they also have a lot of pigment in them which makes my dirty water blending style work well.
The biggest challenge of the model was the face due to the larger scale of the model it takes more shades with the face having reds, purples and other details to add some personality. The narrative I made for this model was of a soldier at the end of a battle, worn and tired and that is what I tried to follow through with painting. When it comes to character models I find it helps to have a little story to assist with colour choices and any weathering or similar details you want to bring to the model.
I would definitely recommend painting 75mm models to help with your painting skills as the larger scale presents a great opportunity to practice glazing, washing, layering and general highlights.
Typically I used a 1:1 ratio of mixing medium and paint for blending up the layers with what I call a "dirty water" mix which allows the highlights to be naturally built up with gradual shading.